In non FGO news, details about the sequel to Extella, Extella Link, are being released. I'll post Famitsu screenshots when I can, but it has the Hakunos wearing explorer outfits, and one of the new Servants is Saber Charlemagne.
Pinning it back to FGO, it seems that there's going to be a bigger push to include Charlemagne's knights: Astolfo is already present, Roland made a cameo in FGO, and Bradamante, the female knight, was leaked to appear in FGO some time in the future.